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For the benefit of 944Hybrids users there are two search functions available for you to use.
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Tach not working Newbie
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Tach not working Newbie
Rond948 Fri May 05, 2023 2:43 pm
86 951 LT1 Swap Renegade circa 2009
Get tach bounce only Tach doesn't read
Have known working cluster when pulled(stock 88 951) is it worth cluster swap to test? or where to start first?
Get tach bounce only Tach doesn't read
Have known working cluster when pulled(stock 88 951) is it worth cluster swap to test? or where to start first?
Rond948- Posts : 68
Join date : 2022-10-06
you need to read this
Gutterboy Fri May 05, 2023 4:19 pm
i hunted for info on this while tearing through every last wire on the harness i inherited on my ls1.
you need to carefully heed the great info on this thread here for a guy who also had an lt1.
i suspect this is a great deal of your issues with the difference of the 8 cylinder signal vs. 4 cylinder signal on ls1 for tach, as well as proper pull down resistor size (prescribed vs. try it and see with 480 ohm).
because you have a bounce i don't think turning it on in your ecu is an issue but maybe worth checking as well?
anyways definitely read all of this and google search under advanced search does wonders.
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you need to carefully heed the great info on this thread here for a guy who also had an lt1.
i suspect this is a great deal of your issues with the difference of the 8 cylinder signal vs. 4 cylinder signal on ls1 for tach, as well as proper pull down resistor size (prescribed vs. try it and see with 480 ohm).
because you have a bounce i don't think turning it on in your ecu is an issue but maybe worth checking as well?
anyways definitely read all of this and google search under advanced search does wonders.
[You must be registered and logged in to see this link.]
Last edited by Gutterboy on Fri May 05, 2023 6:05 pm; edited 1 time in total (Reason for editing : can't figure out how to make the link a different color in font and show up, maybe bold will work)
Gutterboy- Posts : 230
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Re: Tach not working Newbie
Hotrodz of Dallas Mon May 08, 2023 1:43 pm
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Nice link
Gutterboy Mon May 08, 2023 3:01 pm
well done Bob, and exactly why i bought a pack of 1/2W 1000ohm resistors just in case mine doesn't respond as anticipated when i get to that fateful day of first fire in june here (2023, lol)
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Re: Tach not working Newbie
Rond948 Fri May 19, 2023 7:17 pm
This is what I found when investigating tach not working. 200k pententiometer wired to tach. It tested bad so replacement tomorrow. I'll find out but, could this be cause on tach issue? I assume this setup was a early way to fine tune tach(resistor)?[You must be registered and logged in to see this image.]
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Re: Tach not working Newbie
Rond948 Fri May 19, 2023 7:23 pm
BTW, backup cluster tach didn't work and no tach bounce.
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Re: Tach not working Newbie
Hotrodz of Dallas Sat May 20, 2023 10:33 am
Rond948 wrote:BTW, backup cluster tach didn't work and no tach bounce.
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Re: Tach not working Newbie
Rond948 Sat May 20, 2023 12:04 pm
Is resistor in link same for LT1? Do you know if I can use existing 3 wires(pententiometer) in anyway?
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Re: Tach not working Newbie
Hotrodz of Dallas Sat May 20, 2023 1:35 pm
Same resistor. Don't use the pot wiring. Not sure how that was wired. Since you have another gauge cluster, use it instead without the modified wiring.
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Re: Tach not working Newbie
Rond948 Sun May 21, 2023 8:45 am
Can you break this down for me: ls1 link refers to aftermarket tach only? PCM wire colors will be same on lt1 renegade swap? Tach wire color and where? To confirm- original builder confirmed tach did work the way its wired so why would resistor change things?
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Re: Tach not working Newbie
Hotrodz of Dallas Mon May 22, 2023 9:33 am
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You should have this black flat plug in the passenger side footwell. There is a green with black stripe wire in the plug. This is the tach signal wire. This wire will also be in the connector on the back of your gauge cluster. You will need to attach one end of a resistor in  to that wire and the other end of the resistor to any key on 12v wire.
Like this, but using a 1/4 watt, 10k ohm resistor
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You should have this black flat plug in the passenger side footwell. There is a green with black stripe wire in the plug. This is the tach signal wire. This wire will also be in the connector on the back of your gauge cluster. You will need to attach one end of a resistor in  to that wire and the other end of the resistor to any key on 12v wire.
Like this, but using a 1/4 watt, 10k ohm resistor
[You must be registered and logged in to see this image.]
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Newbie tach not working
Rond948 Tue May 23, 2023 9:51 am
Hate to bother, green/blk wire: best tap in location? Footwell? Which side of plug? or cluster tach connector? and easiest 12v key? wire connection location
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Re: Tach not working Newbie
Hotrodz of Dallas Tue May 23, 2023 11:30 am
Rond948 wrote:Hate to bother, green/blk wire: best tap in location? Footwell? Which side of plug? or cluster tach connector? and easiest 12v key? wire connection location
I usually connect at the cluster connector. There will be a switched 12v in that same connector as the green/black wire
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Newbie tach issue
Rond948 Fri May 26, 2023 5:34 pm
Excuse my skills! Temporarily wired in seperate red wire w 10k 1/4 watt resistor between gr/blk and first try: solid red 2nd try red/blk on "B" connector no dice on either of my tachs. No bounce on spare tach but still get bounce on POT wired tach. Are neither solid red or red/blk 12v switched?
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Newbie tach issue
Rond948 Fri May 26, 2023 5:45 pm
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Re: Tach not working Newbie
Hotrodz of Dallas Fri May 26, 2023 5:46 pm
Do you have a multimeter to test for voltage?
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Rond948- Posts : 68
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Confusion on size of resistor.
Gutterboy Sat May 27, 2023 2:45 am
The link I posted in this thread had a guy mention of switching his 1k ohm pull down resistor that didn't work for a 480 ohm and it worked. He also mentioned GM asks for a 5k ohm resistor and Bob recommends a 10k ohm resistor.
Little puzzled at the variations of resistors to add and whether I should halt on my potential add of the 480 ohm.
Also does this pull down always have to be added or do you add after you verify no tach signal happening? Can't recall in my previous read whether it works for some and others have to do this add.
Little puzzled at the variations of resistors to add and whether I should halt on my potential add of the 480 ohm.
Also does this pull down always have to be added or do you add after you verify no tach signal happening? Can't recall in my previous read whether it works for some and others have to do this add.
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Confusion on resistor?
Rond948 Sat May 27, 2023 6:06 am
Bob, in reading ls1 link 1k resistor vs 10k used does this matter? Typo?
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Re: Tach not working Newbie
Hotrodz of Dallas Sat May 27, 2023 10:50 am
Rond948 wrote:Bob, in reading ls1 link 1k resistor vs 10k used does this matter? Typo?
All of them I have had to use a resistor on, i used a 10k. But, i know others have had to uses different sizes. You can try a 1k and see what happens.
Not all cars need this resistor. It depends on the ecu being used. The older 0411's needed a resistor. The later ones didn't.
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Re: Tach not working Newbie
Hotrodz of Dallas Sat May 27, 2023 10:53 am
Rond948 wrote:Embarrassing yes. Walk me thru
Set your meter to dc volts. Attach the ground lead anywhere on metal of the car. Then using the positive lead, probe the connectors for battery voltage. Start with key on. Once voltage is found, turn off and remove the key to see if the voltage goes away. If it does, then that is key on power. If not find another wire with voltage and repeat until you have one that turns off with the key.
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Re: Tach not working Newbie
Gutterboy Sat May 27, 2023 11:14 am
Hotrodz of Dallas wrote:The older 0411's needed a resistor. The later ones didn't.Rond948 wrote:Bob, in reading ls1 link 1k resistor vs 10k used does this matter? Typo?
my motor is a 97 5.7L yet my hptuners scan says the ecu is a 2001 pontiac firebird formula / trans am
how do i know whether mine is a 0411?
if mine is a 0411, i will probably need to get a 1/2W 10kohm resistor since i'd rather just follow your proven way rather than the super old post that a guy used a 480ohm resistor.
i have my ecu vin number from the scan tool from hptuners vcmscanner is there somewhere i can cross reference that serial number with that ecu model number you cited of a 0411? or do i just have to crawl into the passengers foot well and try to read the number?
for additional confusion my pcm pinout matches 99-02 f-body pcm's as per this link
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Re: Tach not working Newbie
Hotrodz of Dallas Sat May 27, 2023 12:15 pm
Gutterboy wrote:Hotrodz of Dallas wrote:The older 0411's needed a resistor. The later ones didn't.Rond948 wrote:Bob, in reading ls1 link 1k resistor vs 10k used does this matter? Typo?
my motor is a 97 5.7L yet my hptuners scan says the ecu is a 2001 pontiac firebird formula / trans am
how do i know whether mine is a 0411?
if mine is a 0411, i will probably need to get a 1/2W 10kohm resistor since i'd rather just follow your proven way rather than the super old post that a guy used a 480ohm resistor.
i have my ecu vin number from the scan tool from hptuners vcmscanner is there somewhere i can cross reference that serial number with that ecu model number you cited of a 0411? or do i just have to crawl into the passengers foot well and try to read the number?
for additional confusion my pcm pinout matches 99-02 f-body pcm's as per this link
[You must be registered and logged in to see this link.]
There should be a label on the outside of the ecu. The part number on it will have 0411 in it. But, that year ecu is a 0411 and is late enough that it shouldn't require the resistor. But, you'll know once its running. Typically, the 97-99 ecus needed the resistor
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Re: Tach not working Newbie
Hotrodz of Dallas Sat May 27, 2023 12:16 pm
Rond948 wrote:Excuse my skills! Temporarily wired in seperate red wire w 10k 1/4 watt resistor between gr/blk and first try: solid red 2nd try red/blk on "B" connector no dice on either of my tachs. No bounce on spare tach but still get bounce on POT wired tach. Are neither solid red or red/blk 12v switched?
Depending on what car your ecu came out of, it might need tach output turned on in the tune.
Hotrodz of Dallas- Posts : 615
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solved my question
Gutterboy Sat May 27, 2023 12:22 pm
looked at service code and indeed my last four numbers are 0411, but since that appears to be a later one i guess i will just roll the dice and see if it works on my day of first fire up.
i'll know exactly what to do and where with connector b under the dash on gauge cluster if so.
it's not possible that the ecu was flashed to a newer program but is still an older unit? like i said engine stamp coincides with being a 97 c5 corvette 5.7L but vcmscanner with hptuners says ecu is 2001 firebird. kind of odd.
perhaps he had ecu reprogrammed for the performance cam he put in it?
i'll be digging into comparing stock LS1 5.7L tune as compares with a download of what's in it today to see what was done for curiouslity. i saw the motor run before it was pulled so nothing to second guess just curious what's changed since cam is quite different than stock at 222/224 lsa 112
and now i'm crazy off topic from original thread... lol
i'll know exactly what to do and where with connector b under the dash on gauge cluster if so.
it's not possible that the ecu was flashed to a newer program but is still an older unit? like i said engine stamp coincides with being a 97 c5 corvette 5.7L but vcmscanner with hptuners says ecu is 2001 firebird. kind of odd.
perhaps he had ecu reprogrammed for the performance cam he put in it?
i'll be digging into comparing stock LS1 5.7L tune as compares with a download of what's in it today to see what was done for curiouslity. i saw the motor run before it was pulled so nothing to second guess just curious what's changed since cam is quite different than stock at 222/224 lsa 112
and now i'm crazy off topic from original thread... lol
Gutterboy- Posts : 230
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Age : 44
Location : calgary, AB
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